New unusual repeated rapid radio eruptions discovered 3 billion light-years away

The cosmic object is distinctive compared to other detections of radio eruptions in recent years, according to new research.

Rapid radio eruptions, or FRBs, are millisecond long eruptions of radio waves in space. Individual radio series broadcast once and are not repeated. But repeated rapid radio eruptions are known to transmit short, energetic radio waves several times.

Astronomers have been able to trace some radio eruptions back to their home galaxies, but they have not yet determined the actual cause of the pulses. Learning more about the origins of these bright, intense radio emissions can help scientists understand what causes them.

Astronomers discovered the object, called FRB 190520, when it released an eruption of radio waves on May 20, 2019. Scientists used the Five-hundred-meter Aperture Spherical Radio Telescope, or FAST, in China, and discovered the eruption in telescope data in November 2019. Then they performed follow-up observations, the astronomers noticed something unusual – the object emitted frequent, repeated eruptions of radio waves.

In 2020, the National Science Foundation’s Karl G. Jansky team used the Very Large Array, or VLA, of telescopes to determine the origin of the eruption before resetting it using the Subaru telescope in Hawaii. Subaru’s observations in visible light showed that the eruption came from the edge of a distant dwarf galaxy.

A study describing the findings published in the journal Nature on Wednesday.

Two identical

The VLA observations also revealed that the celestial the object released ever weaker radio waves between the repeated eruptions. It is very similar to just one other known repeated fast radio series: FRB 121102, discovered in 2016.

The first detection and subsequent tracing of FRB 121102 back to the point of origin in a small dwarf galaxy more than 3 billion light-years away was a breakthrough in astronomy. It was the first time astronomers were able to learn about the distance and environment of these mysterious objects.

“Now we actually have to explain this double mystery and why FRBs and persistent radio sources are sometimes found together,” said co-author Casey Law, a staff researcher in radio astronomy at the California Institute of Technology. “Is it common when FRBs are young? Or maybe the object that creates the eruptions is a massive black hole that eats up a neighboring star? Theorists have much more detail to work with now, and the possibility of explanation is shrinking.”

Currently, less than 5% of the hundreds of identified rapid radio eruptions have been known to recur, and only a few of them are regularly active.

But FRB 190520 is the only persistently active, meaning it has never “turned off” since it was discovered, said study author Di Li, chief of the National Astronomical Observatories of China’s radio station and the FAST Operation Center. Meanwhile, FRB 121102, “the first known repeater, can shut down for several months,” Li said.

New questions

The latest findings raise several questions because astronomers are now wondering if there could be two types of rapid radio eruptions.

“Are those who repeat different from those who do not? What about the persistent radio radiation – is it common?” said co-author Kshitij Aggarwal, who was involved in the study as a doctoral student at West Virginia University, in a statement.

Hundreds of mysterious rapid radio eruptions discovered in space

It is possible that there are different mechanisms that cause radio outbreaks, or that what produces them behaves differently during different stages of evolution.

Previously, scientists have assumed that rapid radio eruptions are caused by the dense remnants left behind by a supernova, called a neutron star, or neutron stars with incredibly strong magnetic fields called magnetars.

This is an artist's concept of a neutron star with an ultra-strong magnetic field, called a magnetar, which emits radio waves (in red).

FRB 190520 is considered a possible “newborn” object because it was in a crowded environment, Law said. This environment can be caused by material released by a supernova, which resulted in the formation of a neutron star. As this material spreads over time, the eruptions from FRB 190520 may decrease as it ages.

Going forward, Li wants to detect more rapid radio eruptions.

“A coherent picture of the origins and evolution of FRBs is likely to emerge in just a few years,” Li said.

Law is excited about the implications of having a new class of radio wave sources.

“For decades, astronomers believed that there were basically two types of radio sources that we could see in other galaxies: increasing supermassive black holes and star-forming activity,” said Law. “Now we say that there can be no either / or categorization anymore! There is a new child in the city, and we should consider that when we study populations of radio sources in the universe.”